Green’s Dictionary of Slang

1. (US campus) sexually involved (with).

1989		G Tate ‘The GOP Throws a Mammy-Jammy’ in Flyboy in the Buttermilk (1992) 105: Eldridge Cleaver might have interpreted this as saying to Atwater, ‘Yo, boy, if you gonna get all up in our music, then I can get all up into your women’.
1997–2000		Da Bomb 🌐 all up in (someone) (phr) To be sexually involved with someone. Don’t mack on him; he’s all up in Katie. [Peabody Conservatory, Baltimore, MD].

2. (US teen) interfering, involved in.

1989		see sense 1.
2002		Teen Lingo: The Source for Youth Ministry 🌐 all up in my biznezz when someone is meddling in your affairs or dealings. They are ‘in your business.’ ‘Quit asking about my girl ... why you all up in my biznezz?’.
2006		G. Iles Turning Angel 389: He’s all up in that dope, just like most of these young no-goods.
2017		D. Winslow The Force [ebook] ‘You stay out of that’ [...] ‘No, I’m going to be all up in that’.
2022		J. Hannaham Didn’t Nobody Give a Shit 109: I don’t know who said you [i.e. one’s conscience] could be in my head an all up in my shit anyway.